Anesthetics Flashcards
Goal of general anesthesia
amnesia
analgesia
immobilization
Inhaled anesthetic properties
cross BBB
Lipid solubility - higher = more potent
blood solubility - lower = more rapid onset of action
-doens’t get “stuck in the blood”
Minimum alveolar concentration (MAC)
concentration of inhaled anesthetic needed to prevent movement in 50% of patients after painful stimulus
Inhaled anesthetic drugs
Nitrous oxide
- low blood solubility (rapid induction), low lipid solubility (low potency)
- block NMDA receptors
- rapid onset/rapid recovery
Halothane
- high blood solubility (long induction)
- hepatotoxicity
- long to start, long to recover
Sevoflurane, desflurane
- low blood solubility, high lipid solubility
- potent, most used
Isoflurane
-moderate blood and lipid solubility
Propofol
IV anesthetic
increases GABA
Rapid onset, rapid recovery (20-40min)
high triglyceride count - risk acute pancreatitis with prolonged use
“milk of amnesia”
maintenance in IV drip
Ketamine
IV anesthetic
dissociative anesthetic
hallucinations in high doses in adults
increases cerebral blood flow
use: analgesia, conscious sedation, induction
Barbiturates
IV anesthetics
Phenobarbital - increases liver enzyme synthesis (used in Crigler Najjar type II)
Pentobarbital
secobarbital
Thiopental (important in brain surgery)
increase duration of Cl- channel opening on GABA receptors
SE:
sedation, CNS depression, sluggish, ataxic gait, double vision
Overdose: tx sx, no antidote
Benzodiazepines
IV anesthetics
Diazepam
lorazepam
alprazolam
Midazolam - MC used for conscious sedation
Others:
Temazepam - insomnia - long acting
Chlordiazepoxide - etOH withdrawal
Increase frequency of Cl- channel opening on GABA receptors
Reverse w/ flumazenil (can trigger withdrawal seizure)
mnemonic for barbiturate and benzodiazepine MOA
“Ben likes it more frequently, Barb likes it to last longer”
effects on Cl- channel on GABA receptors
Opioids used as IVE anesthetics
morphine
fentanyl (doesn’t induce histamine release, not as itchy as with morphine)
remifentanil
sufentanil
Analgesia
mu, delta, kappa receptors
Butorphanol
partial opioid
causes respiratory depression
Dextromethorphan
weak opioid used for cough suppression
Tramadol
less addictive opioid used for analgesia
Loperamide, diphenoxylate
treatment of diarrhea
Naloxone, naltrexone
opioid receptor antagonists
reverse opioid overdose
Endogenous agonists of mu, delta, kappa receptors
Mu - beta-endorphin
Delta - enkephalin
Kappa - dynorphin
Non-depolarizing NM blocking agents
tubocurarine atracurium mivacurium vecuronium rocuronium pancuronium
Competitive inhibitors of postsynaptic nicotinic acetylcholine receptors at NMJ
can reverse w/ acetylcholinesterase inhibitor - neostigmine
Depolarizing NM blocking agent
succinylcholine
causes muscle fasciculations
Phase 1: rapid onset and recovery, cannot be reversed - 10 min
Phase 2: larger dose, longer recovery - can be reversed w/ AChEI - lasts 20-30 minutes up to hours
Succinylcholine + inhaled anesthetic in patient with RYR1 gene mutation –> malignant hyperthermia
Tx: cool patient, sedate, dantrolene (block release of Ca2+ from SR)
Local anesthetics
Lidocaine, procain, cocaine
block Na+ channels
Don’t work well in acidic tissues - infected tissues
give w/ local vasoconstrictor (epi)
- except in terminal organs (eg fingers - no collateral circulation = ischemia)
- don’t need as much anesthetic, reduces bleeding
Order of blockade for local anesthetics
small myelinated
small unmyelinated
large myelinated
